1. Field of the Invention
This invention relates to a process for the destruction of a variety of toxic agents including sulfur and nitrogen mustard gas and Lewisites using the superoxide ion in deep eutectic solvents.
2. Background of the Related Art
In recent years with the global emphasis on the reduction of the huge stockpile of chemical warfare agents, the art has been confronted with the problem of safely destroying and disposing of a variety of obsolescent chemical warfare agents, e.g., mustard gas and Lewisite. Large quantities of chemical warfare agents, in various forms, are contained in a wide spectrum of munitions ranging from tactical ordnance to ballistic missiles, while equally large quantities are found in storage vessels with capacities ranging from a few grams to several tonnes. The problem of treatment and disposal is, therefore, severely complicated, not only by the extreme toxicity of infinitesimal quantities of these agents, but also by the need to simplify their recovery and to minimize the number of transfer and handling steps.
The Chemical Weapons Convention was adopted by the Conference on Disarmament in Geneva on Sep. 3, 1992, entered into force on Apr. 29, 1997, and calls for a prohibition of the development, production, stockpiling and use of chemical weapons and for their destruction under universally applied international control. Eliminating the hazard of chemical warfare agents is desirable both in storage sites and on the battlefield. The United States ratified the convention in 1997.
In August 2006 the United States of America announced that it destroyed half of all chemical weapons in its stockpile. That includes bombs, rockets, mortars, projectiles, land mines and spray tanks filled with nerve agents (including sarin and VX), plus blister agents (including mustard gas). The total destroyed to date represents 39 percent of the U.S. stockpile by weight.
To accomplish the destruction of half of the national stockpile, the Chemical Materials Agency had to overcome permitting delays and facility work stoppages, it said. In particular, the agency stated, “delays resulted from the challenges associated with obtaining, modifying and/or closing environmental permits.” There were also unexpected facility work stoppages to evaluate and correct problems.
In July 2006, the United States submitted a draft request to the Executive Council of the Organization for the Prohibition of Chemical Weapons that would extend the deadline for the destruction of the entire U.S. chemical weapons stockpile from April 2007 to April 2012. Currently, all of the mustard gas that has been produced for military purposes will be destroyed by either incineration or neutralization. However, complete destruction of the entire stockpile of mustard gas may take long time. Mustard gas is now being stored in military depots and storage facilities.
Sulfur mustard (SM), chemically known as 1,1′-thiobis-(2-chloroethane) and nitrogen mustards Bis(2-chloroethyl)ethylamine (HN1), Bis(2-chloroethyl)methylamine (HN2), Tris(2-chloroethyl)amine (HN3) are highly toxic and persistent liquid vesicants.
An important aspect of any containment strategy is to be able to neutralize the threat using chemical decontamination methods. Most chemical warfare agents (CWA's) can be destroyed or rendered harmless by suitable chemical treatments.
Where the technique of incineration is permitted, certain of warfare agents, including mustard gas and the nerve gases, may be totally destroyed through thermal oxidation, since the products of combustion, e.g., sulfur dioxide, may be readily contained and prevented from escaping to the atmosphere.
On the other hand, the Lewisites, [i.e., dichloro(2-chlorovinyl)arsine, bis(2-chlorovinyl)chloroarsine and tris(2-chlorovinyl)arsine], which comprises approximately 36 weight percent arsenic, upon combustion produce the highly toxic arsenic trioxide. Under conditions normally experienced in incinerator operation, it is extremely difficult to limit the release of this contaminant to the atmosphere at acceptably low rates.
Processes known in the art for destruction of pure SM and HN consist of high temperature reaction technology, which involve destruction by heating at high temperature. The technologies are incineration, pyrolysis, plasma torch and molten metal systems. Among all these high temperature reaction technologies, incineration is a well-proven technology for the destruction of pure SM and HN and is widely used for the destruction of pure SM and HN.
The main disadvantages of incineration are that it consumes a lot of energy and it may produce toxic products.
Another known process in the art for destruction of pure SM and HN is the low temperature destruction technology based on hydrolysis of SM and HN.
The main disadvantage of the technology involving hydrolysis is that it uses many hazardous chemicals for the destruction process.
Another known process in the art for destruction of pure SM is the low temperature destruction technology based on electrochemical oxidation. In this process SM is oxidized in Ag(II)/Ag(I) electrochemical cell in acidic medium.
The main drawback of this technology based on electrochemical oxidation is that one or two of the products are toxic in nature. Another drawback of this technology based on electrochemical oxidation is that it cannot be used for bulk destruction of pure SM.
Still another drawback of this technology based on electrochemical oxidation is that the cost involved is very high.
Another known process in the art for destruction of pure SM is the low temperature destruction technology based on solvated electron system in which pure SM is reduced by solution of metallic sodium in anhydrous liquid ammonia.
The main disadvantage of the above low temperature destruction process based on solvated electron system is that it requires precise conditions for the use of highly reactive metallic sodium. Since hydrogen chloride is present in SM, HN1, HN2, and HN3 it may lead to uncontrollable exothermic (highly flammable) reaction.
Another known process in the art of destruction of mustard gas is the low temperature destruction technology based on chemical conversion using thiophilic agents.
The major drawback of the destruction process based on thiophilic agents is that this method is suitable only for pure mustard gas. Since stock piles of mustard gas contain impurities in different concentrations, the said method cannot be used for the efficient destruction of mustard gas.
One of the present standard decontaminating means of SM is a solution of DS-2, which is composed of, on a weight basis, 70% diethylenetriamine, 28% 2-methoxyethanol and 2% sodium hydroxide. DS-2 reacts rapidly with mustard gas via proton abstraction leading to dehydrochlorination of the mustard gas to form divinylsulfide. DS-2, however, is not widely applicable since it is corrosive to metals and incompatible with a number of polymers, e.g. Laxan, polyvinyl chloride, cellulose acetate, acrylic, Mylar.
Although the hydrolysis approach for the treatment of Lewisite, especially at somewhat elevated temperatures, is capable of effectively destroying virtually all of the principal Lewisite specie, known as Lewisite I, the associated species, Lewisite II and Lewisite III (previously generically-termed “the Lewisites”) are considerably more resistant to hydrolysis and will survive this treatment. The secondary species, though milder vesicants than the principal analogue, are nonetheless toxic and cannot be tolerated as a component of the reaction products.
Another undesirable feature of the hydrolysis procedure is the formation of a trivalent arsenic compound, sodium arsenite which represents one of the most toxic forms of arsenic.
Moreover, since this product is extremely soluble, some considerable difficulty is encountered in achieving its secure, permanent disposal.
A second popular approach suggested in the literature involves oxidation of the Lewisite with the aid of some oxidizing agent, e.g., sodium hypochlorite (NaOCl), chlorine (Cl2), hydrogen peroxide (H2O2) or nitric acid (HNO3).
Although complete oxidation may be possible with the nitric acid, reagents, e.g., hypochlorites and peroxides were, under the conditions investigated, found to be capable of only partial oxidation.
In each instance, a final product of the reaction is a chlorovinyl arsonic acid which, though less noxious than the original Lewisite, is nevertheless highly toxic and represents a significant final disposal problem.
It should be noted that products analogous to the arsonic acid produced by the oxidation of Lewisite I are derived from similar oxidations of Lewisite II and Lewisite III and that these constitute comparable disposal problems.
United States Statutory Invention Registration H223 disclosed a method of decontaminating articles and/or structures contaminated with or expected to be contaminated with mustard gas by treating the articles and/or structures with a transition metal complex of a tetrasulfonated or tetramino phthalocyanine catalyst which binds oxygen from the air and converts the oxygen to superoxide. The superoxide dehydrochlorinates the mustard gas to divinylsulfide. Articles and/or structures amenable to such treatment are buildings, military vehicles, artillery weapons, tents, clothes and the like. However, this method is not suitable for mustard gas stored as liquid in containers.
U.S. Pat. No. 6,569,353 disclosed a universal decontamination formulation and method for detoxifying chemical warfare agents (CWA's) and biological warfare agents (BWA's) without producing any toxic by-products, as well as, decontaminating surfaces that have come into contact with these agents. The formulation includes a sorbent material or gel, a peroxide source, a peroxide activator, and a compound containing a mixture of KHSO5, KHSO4 and K2SO4. The formulation is self-decontaminating and once dried can easily be wiped from the surface being decontaminated. A method for decontaminating a surface exposed to chemical or biological agents was also disclosed.
U.S. Pat. No. 7,214,836 disclosed methods and kits for decomposing organophosphorus compounds in non-aqueous media at ambient conditions. It was claimed that insecticides, pesticides, and chemical warfare agents can be quickly decomposed to non-toxic products. The method comprised combining the organophosphorus compound with a non-aqueous solution, preferably an alcohol, comprising metal ions and at least a trace amount of alkoxide ions.
U.S. Pat. No. 7,125,497 disclosed decontamination formulations for neutralization of toxic industrial chemicals, and methods of making and using same. It was claimed that these formulations are effective for neutralizing malathion, hydrogen cyanide, sodium cyanide, butyl isocyanate, carbon disulfide, phosgene gas, capsaicin in commercial pepper spray, chlorine gas, anhydrous ammonia gas; and may be effective at neutralizing hydrogen sulfide, sulfur dioxide, formaldehyde, ethylene oxide, methyl bromide, boron trichloride, fluorine, tetraethyl pyrophosphate, phosphorous trichloride, arsine, and tungsten hexafluoride. U.S. Pat. No. 7,102,052 disclosed a method for the neutralization of some chemical agents. In this method hydrogen peroxide is vaporized and mixed with ammonia gas in a ratio between 1:1 and 1:0.0001. The peroxide and ammonia vapor mixture are conveyed to a treatment area to neutralize V-type, H-type, or G-type chemical agents, pathogens, biotoxins, spores, prions, and the like. The ammonia provides the primary deactivating agent for G-type agents with the peroxide acting as an accelerator. The peroxide acts as the primary agent for deactivating V-type and H-type agents, pathogens, biotoxins, spores, and prions. The ammonia acts as an accelerator in at least some of these peroxide deactivation reactions.
U.S. Pat. No. 7,070,773 disclosed compositions effective in decontaminating either biological pathogens or both chemical and biological pathogens. These compositions are particularly suitable for the decontamination of biological warfare agents or both chemical and biological warfare agents. The compositions comprise generally a blend of biocides, and may additionally comprise a protein and an enzyme. Further, the composition is contained in a buffered foam forming material for ease in distribution. The compositions are nontoxic, noncorrosive and nonflammable.
U.S. Pat. No. 7,037,468 disclosed an apparatus and method for using a non-thermal plasma or corona discharge generated at multiple points and distributed to decontaminate surfaces and objects contaminated with chemical or biological agents. The corona discharge can be generated using very short high voltage pulses. The pulsed corona discharge can be directed at a contaminated surface through the unbraided strands at an end of a dielectric covered conductor. Another pulsed discharge embodiment incorporates a primary coil surrounding a chamber having a void filled with a plurality of secondary coils. A silent corona discharge can be generated using a variety of different configurations of a dielectric coated electrode and a bare electrode.
WO/1998/016332 patent disclosed improved methods for the treatment of liquid chemical compounds and process systems for practicing those methods. The methods are practiced by spraying the liquid chemical compounds into a matrix bed of heat resistant materials at temperatures sufficiently high to oxidize the chemical compounds. The sprayed liquid chemical compound is preferably heated to its gaseous state prior to contacting the matrix bed. Processing steps for removing coke deposits in the matrix bed are also provided. The methods are particularly advantageous for the destruction of chemical agents and munitions. U.S. Pat. No. 5,545,799 disclosed a sequential process for the destruction of a toxic organic chlorine-containing compound, especially a chlorine- and arsenic-containing compound e.g., a Lewisite or a mustard gas. The process includes the first step of carrying out an oxidizing reaction between the chlorine-containing compound, and an oxidizing agent, especially hydrogen peroxide, while maintaining the temperature and the pH within pre-selected ranges e.g., about 50° C. to about 90° C. and the pH starting at about 1 to about 2 during the oxidation and terminating at about 5 to about 8 to provide an oxidation product of the original toxic organic chlorine-containing compound, original toxic chlorine- and arsenic-containing compound. After completion of the oxidizing reaction, any residual oxidizing agent is preferably catalytically decomposed. Then, the oxidation product of the original toxic organic chlorine-containing compound, is decomposed at an alkaline pH, e.g., to a maximum final pH of about 11 to provide an inorganic compound, e.g., an inorganic arsenic-containing compound. Such compound can easily and safely be disposed of.
U.S. Pat. No. 6,479,723 disclosed a process for the chemical destruction of sulfur mustard by chemical conversion that comprises in the step of reacting sulfur mustard with a thiophilic agent prepared by dissolving sulfur in ethylene diamine and/or ethanol diamine.
A new class of compounds, ionic liquids (ILs) has emerged in the last ten years that may become a key ally in meeting the twin challenges of efficient and environmentally benign chemical processing. They have the potential to revolutionize the way we think of and use solvents. The reason is that they act like good organic solvents, dissolving both polar and nonpolar species. In many cases, they have been found to perform better than commonly used solvents. In addition, ionic liquids are non-flammable and non-volatile. The wide and readily accessible range of ionic liquids with corresponding variation in physical properties offers the opportunity to design an ionic liquid solvent system optimized for a particular process.
A key feature of ionic liquids is that their physical and chemical properties can be tailored by judicious selection of cation, anion, and substituents. For example, a choice of anions such as halide (Cl−, Br−, I−) nitrate (NO3−), acetate (CH3CO2−), trifluoroacetate (CF3CO2−), triflate (CF3SO3−) and bis(trifluoromethylsulfonyl)imide (CF3SO2)2N−) can cause dramatic changes in the properties of ionic liquids. The water solubility of the ionic liquid can be controlled by the nature of the alkyl substituent on the cation. Increasing the length of the alkyl chain tends to decrease water solubility by increasing the hydrophobicity of the cation.
ILs, however, are quite difficult to make, very expensive, and their toxicity has not yet been ascertained. Accordingly, none of these compounds has been registered and this currently limits their wide-scale use. In addition, only a small number of ILs is being produced in commercial quantities.
A deep eutectic solvent (DES) is a type of ionic solvent with special properties composed of a mixture which forms a eutectic with a melting point much lower than either of the individual components. The first generation eutectic solvents were based on mixtures of quaternary ammonium salts with hydrogen donors such as amines and carboxylic acids. The deep eutectic phenomenon was first described in 2003 for a 1 to 2 by mole mixture of choline chloride (2-hydroxyethyl-trimethylammonium chloride) and urea. Choline chloride has a melting point of 302° C. and that of urea is 133° C. The eutectic mixture however melts as low as 12° C.
This DES is able to dissolve many metal salts like lithium chloride (solubility 2.5 mol/L) and copper(II) oxide (solubility 0.12 mol/L). In this capacity, these solvents could be applied in metal cleaning for electroplating. Because the solvent is conductive, it also has a potential application in electropolishing. Organic compounds such as benzoic acid (solubility 0.82 mol/L) also have great solubility and this even includes cellulose (filtration paper). Compared to ordinary solvents, eutectic solvents also have a very low VOC and are non-flammable. Other deep eutectic solvents of choline chloride are formed with malonic acid at 0° C., phenol at −40° C. and glycerol at −35° C.
Compared to ionic liquids that share many characteristics but are ionic compounds and not ionic mixtures, deep eutectic solvents are cheaper to make, much less toxic and sometimes biodegradable.
WO 2002 026381 disclosed an invention relates to ionic compounds and methods for their preparation. In particular, the invention relates to ionic compounds comprising hydrated metal salts, which are liquid at low temperatures, generally below about 100° C.
WO 02/26701 A2 disclosed a method for the synthesis of DES compounds with a freezing point of up to 100° C. by the reaction of one amine salt (I), such as choline chloride with an organic compound (II) capable of forming a hydrogen bond with the anion of the amine salt, such as urea, wherein the molar ratio of Ito II is from 1:1.5 to 1:2.5. The DES compounds are useful as solvents, and electrolytes for example in electroplating, electrowinning, electropolishing, and as catalysts.
WO 00/56700 disclosed a method for the synthesis of DES having a melting point of no more than 60° C., formed by the reaction of a quaternary ammonium compound or a mixture of two or more thereof; with a halide of zinc, tin or iron, or a mixture of two or more thereof.
We were the first to show that a stable superoxide ion can be generated in ILs [AlNashef et al. Ph. D. Dissertation, 2004]. We also showed that hexachlorobenzene could be destroyed by the reaction of the superoxide ion generated in selected ILs.
From what was mentioned above, it is clear that there is a need for a viable decontamination method that is inexpensive, occurs at ambient temperature, and most importantly, benign.